1. Field of the Invention
The present invention relates to a low-profile and small-sized variable resistor, and more particularly, to the structure of the external connection portion of a metallic terminal that is insert-molded in a board.
2. Description of the Related Art
As a known example of a variable resistor, Japanese Unexamined Patent Application Publication No. 9-223608 discloses a variable resistor wherein a first metallic terminal having a grommet is insert-molded in a board, second metallic terminals are also insert-molded in the board. A substantially arcuate resistor conductive to the second metallic terminal is provided on the top surface of the board. A slider having a drawn portion with a hole provided at the center thereof is fitted to the grommet of the first metallic terminal. The grommet is caulked in a outwardly opened state, and thereby the slider is rotatably installed on the board to be being electrically connected with the first metallic terminal. A contact arm portion sliding on the resistor, and an adjusting portion rotationally operated with a tool such as a driver, are integrally provided with the slider.
In the above-described variable resistor, since the external connection portions of the first and second metallic terminals are constructed to be led out of the bottom of the board, and folded upwardly toward the top surface side, the product can be made low-profile, and soldering of the external connection portions to the board is facilitated.
When bending is performed with respect to the external connection portions of the metallic terminals, bending stresses are concentrated on the board portions holding the external connection portions. However, once the external connection portions of the metallic terminals are led out along the bottom of the board as described above, the terminal holding power of the board is reduced, such that the metallic terminals generate looseness. In particular, since one end portion of each of the second metallic terminals is exposed on the top surface of the board, and this exposed portion is electrically connected with the resistor provided on the top surface of the board, the occurrence of the loose metallic terminals causes an unstable electrical connection between the metallic terminals and the resistor, and deteriorates the characteristics of this variable resistor.